Does DSLR suffer from Reciprocity law failure?


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roygoh

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#5
Hi Daniel,

Welcome to Clubsnap.

I have merged your 2 threads of the same title, as we discourage cross posting.

You should only post a topic once in the appropriate sub-forum. Posting the same topic in multiple forums does not help improve the visibility, but creates clutter and scatters the information/discussion.

Thanks!

- Roy
 

lsisaxon

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Nov 29, 2004
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#6
hazekang said:
wat will fail? :dunno:
It means that the exposure time is no longer just double for every stop like it is when you use for normal exposures. In film photography, for longer exposures, you will need more than double the exposure time to get a one stop increase in exposure.
 

lsisaxon

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#8
hazekang said:
wow, does the cam metering noe this?
Unfortunately, no. And the amount to compensate varies from film to film.. That's why it's called a failure. For professional film where it is expected to be used in situation where long exposure might be used, the documentation will talk about this and the amount to compensate for.

See section 5 of this documentation for the Fuji NPH400 film. That's to compensate for reciprocity failure.
http://www.silverprint.co.uk/PDF/NPH400.pdf
 

zac08

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roygoh said:
Hi Daniel,

Welcome to Clubsnap.

I have merged your 2 threads of the same title, as we discourage cross posting.

You should only post a topic once in the appropriate sub-forum. Posting the same topic in multiple forums does not help improve the visibility, but creates clutter and scatters the information/discussion.

Thanks!

- Roy
PS : there's one more in Kopitiam...
 

justarius

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#11
Reciprocity failure is a characteristic of film during super long exposures. DSLR don't use film, so this law wouldn't affect DSLRs. What DSLR will suffer from during super long exposures are hot pixels.
 

Ah Pao

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#12
justarius said:
Reciprocity failure is a characteristic of film during super long exposures. DSLR don't use film, so this law wouldn't affect DSLRs. What DSLR will suffer from during super long exposures are hot pixels.
...and higher noise levels.
 

Clown

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#13
justarius said:
Reciprocity failure is a characteristic of film during super long exposures. DSLR don't use film, so this law wouldn't affect DSLRs. What DSLR will suffer from during super long exposures are hot pixels.
actually it means when the film fail to react to very low light levels, esp with low ASA films.. or in other words, the amount of light present at the moment is not enuff to cause a reaction with the film particles, so more time is needed for the film to be exposed correctly.
 

Ah Pao

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sORe-EyEz said:
so diff image sensor got diff value? :dunno:
With the detailed description of what the reciprocity law failure is in the posts above, I hope you've caught the fact that DIGITAL CAMERAS do not suffer from this failure.

So your question is basically invalid. :sweat:
 

iria

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#16
justarius said:
Reciprocity failure is a characteristic of film during super long exposures. DSLR don't use film, so this law wouldn't affect DSLRs. What DSLR will suffer from during super long exposures are hot pixels.
agreed..

i say.. the maker should come out with a setting that can reduce it. anyway to what i think, Reciprocity failure for film is similar to hot pixels.

In this case.. we can adjuct the setting to minimize the Reciprocity failure.

but for DSLR.. we cant..
 

Ah Pao

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#17
Reciprocity failure is not akin to hot pixels in digicams.

For example, you are taking a picture of a moon-lit rock. You've selected an exposure of 5 minutes @ F/2.8 (it's a hypothetical combination).

If you selected an shutter speed + f-stop combination of 10 minutes @ F/4 or 20 minutes @ F/5.6, it should give you the same exposure.

However, with such long exposure, because of the chemical nature of silver halide film emulations, it suffers from a reciprocity failure beyond a certain shutter speed. At F/5.6, you'll need to set your shutter speed longer than 20 minutes in order to get a proper exposure.

Datasheets of film will usually state the compensation needed for exposures past the reciprocity failure point.

For digital, it does not suffer from such failure. 5 min @ f/2.8, 10 min @ f/4 and 20 min @ f/5.6, etc. will yield the same exposure (change in DOF not withstanding, of course).
 

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